<template>
  <div class="pagination">
    <button :disabled="pageNo===1" @click="$emit('getPageNo',pageNo-1)">上一页</button>
    <button v-show="startNumAndEndNum.start>1" @click="$emit('getPageNo',1)" :class="{active:pageNo===1}">1</button>
    <button v-show="startNumAndEndNum.start>2">···</button>
    <!--  中间部分-->
    <button v-for="(page,index) in startNumAndEndNum.end" :key="index" v-show="page>=startNumAndEndNum.start" @click="$emit('getPageNo',page)" :class="{active:pageNo===page}">{{page}}</button>

    <button v-show="startNumAndEndNum.end<totalPage-1">···</button>
    <button v-show="startNumAndEndNum.end<totalPage" @click="$emit('getPageNo',totalPage)" :class="{active:pageNo===totalPage}">{{totalPage}}</button>
    <button :disabled="pageNo === totalPage" @click="$emit('getPageNo',pageNo+1)">下一页</button>

    <button style="margin-left: 30px">共 {{total}} 条</button>
    <!-- <div>{{startNumAndEndNum.end}}/{{startNumAndEndNum.start}}</div> -->
  </div>
</template>

<script>
export default {
  name: "Pagination",
  props:['pageNo','pageSize','total','continues'],
  computed:{
      totalPage(){
        return Math.ceil(this.total/this.pageSize)
      },
      //计算连续的页码起始数字与结束数字
      startNumAndEndNum(){
          let start=0,end=0;
        // 连续的页码数字至少5页，如果出现不够5页
        if(this.totalPage< this.continues){
            start = 1;
            end = this.totalPage
        }else{
            // 否则够了5页(正常页面)
            start = this.pageNo - Math.floor(this.continues/2)
            end = this.pageNo + Math.floor(this.continues/2)
            // 出现不正常现象[页码头为12345]
            if(start<1){
                start = 1
                end = this.continues
            }
            // 页码尾部27 28 29 30 31
            if(end>this.totalPage){
                start = this.totalPage - this.continues + 1
                end = this.totalPage
            }
        }
        return {start,end}
      }
  }
};
</script>

<style lang="less" scoped>
.pagination {
    text-align: center;
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #409eff;
      color: #fff;
    }
  }
}
.active{
  background-color: skyblue;
}
</style>
